1. Technical Field of the Invention
This invention relates to radio telecommunication systems and, more particularly, to a system and method of rapidly locating a mobile station by simultaneously paging in a plurality of exchanges.
2. Description of Related Art
In existing radio telecommunications networks, a metropolitan area may be covered by a plurality of mobile switching centers (MSCs). The service area of each MSC is referred to herein as an exchange. By regulation, one of the MSCs in the metropolitan area is provided with a roamer port. A roamer port is a local telephone number through which local callers in the metropolitan area may call a subscriber from a long distance exchange who has roamed into the metropolitan area. Local callers, thereby, may avoid long distance charges while the roaming subscriber is operating in the metropolitan area.
When a call to the roaming subscriber comes through the roamer port, a mechanism is needed to locate the roaming subscriber who may be roaming within any of the metropolitan exchanges within the roamer port region. In existing radio telecommunications networks, a process known as sequential paging is utilized. In an exemplary existing metropolitan area, there may be 4 local MSCs, (MSC-1 through MSC-4) with the roamer port defined in MSC-1, and a roaming mobile station located in MSC-4. When a roamer port call is received in MSC-1, MSC-1 begins to page for the mobile station in its service area. Paging within MSC-1 may take as long as 12 seconds. If MSC-1 does not receive a page response from within its service area, MSC-1 seizes a trunk and routes the call to MSC-2. This action may take another 1 or 2 seconds. MSC-2 then pages the mobile station in its service area. This process may continue sequentially through each MSC until MSC-4 receives a page response from the mobile station. The total time from receipt of the call in MSC-1 until MSC-4 receives a page response may be as long as 40 seconds, with three inter-exchange trunks seized.
There are several problems with the sequential paging process. First, the sequential paging process is excessively long, and the calling subscriber often hangs up before the paging process can be finished and the call is delivered. Second, the use of system resources is not optimized since inter-exchange trunks must be seized in order to move the paging process to successive MSCs. Third, the sequential paging process produces an uneven paging load in the MSCs in the metropolitan area. MSC-1, in which the roamer port is implemented, has the highest paging load since it must page for every roamer port call. The paging load is progressively lighter in each subsequent MSC.
Although there are no known prior art teachings of a solution to the aforementioned deficiency and shortcoming such as that disclosed herein, U.S. Pat. No. 5,153,902 to Buhl et al. (Buhl) discusses subject matter that bears some relation to matters discussed herein. Buhl discloses a multi-exchange paging system for locating a mobile telephone in a wide area telephone network. In Buhl, a call from the Public Switch Telephone Network (PSTN) is first routed to a gateway mobile switching center (G-MSC). The G-MSC then interrogates a home location register (HLR) for location information regarding the mobile station. The HLR sends, either sequentially or simultaneously, requests to multiple MSCs to locate the mobile station. MSCs which are unsuccessful in locating the mobile station return "no-page-response" messages to the G-MSC. The MSC which has successfully paged the mobile station returns a routing number to the G-MSC. The G-MSC then routes the call to the successful MSC.
Buhl, however, requires the use of a HLR. If the mobile station is from a foreign network, the HLR associated with the mobile station will require long distance signaling from the G-MSC. Long distance interrogation of HLRs is not acceptable to system operators for roamer port calls. Buhl does not teach or suggest a system or method of multi-exchange location without utilizing a HLR.
Review of the foregoing reference reveals no disclosure or suggestion of a system or method such as that described and claimed herein.
In order to overcome the disadvantage of existing solutions, it would be advantageous to have a multi-exchange paging system that simultaneously pages for a mobile station in a plurality of exchanges without utilizing a home location register. The present invention provides such a system and method.